Newer operating systems often times feature transparent window borders and in some cases transparent windows. Window transparency can often interfere with alpha-blending because of the difficulties posed by trying to alpha-blend an image to the desktop. In fact, most alpha-blending techniques do not interact with the desktop or other windows, but rather alpha blend two images. Therefore it can be difficult to anti-alias the corners of windows so that they appear smooth when contrasted against a background or other windows.